Tank Size Availability

Getting back into aquariums after 20 years and have a tank size question.

My knowledge is so out of date, I am essentially a beginner.

Been looking at purchasing a 90 gallon tank (48 inch length is my limit). I inquired at a store and was told that certain sizes have fallen out of favor with manufacturers. 90 gallons being one of them. Basically, the said that most common are 55, 75 and then a jump to 125 (too big). That locating a large tank outside those ranges is tough. Locating a extra-tall or extra-high (30 inches vs. 24 inches) tank is even worse.

Is that true? I was going to bide my time and try to locate one used, but was wondering whether a 90 gallon tank or an extra-tall tank is really that hard to come by. The stores could have just been stating it to convince me to buy a size they had in stock.

Thanks.

- Jason